1. Field of the Invention
The present invention relates to a filtration mask, such as an emergency hood.
2. Summary of the Prior Art
Filtration masks have been known for many years, and their configuration depends on their intended use. Simple filtration masks, such as surgical masks that are used by doctors or surgeons, in order to protect patients from germs contained in their breath, cover only the wearer's nose and mouth. They may be formed entirely from filtration material. Similar masks are used by wood workers and construction workers etc, to prevent dust particles entering their respiratory systems.
More complex filtration masks have been developed particularly for use in military conflicts, to provide protection for e.g. soldiers against chemical or biological hazards. These masks are often known as respirators, and usually employ a rubber mask section which covers the wearer's face, and acts as a housing for air filters. These masks must seal effectively around the face of the wearer, to ensure that no hazardous vapours can enter the wearer's respiratory system by routes other than via the air filters. The masks are often cumbersome, expensive, and must be sized to the particular wearer, in order to provide an effective seal around the periphery of the wearer's face.
Intermediate these two types of masks are emergency hoods. Emergency hoods are a type of respirator, also called an “escape hood”, which are designed to assist escape from CBRN hazards, and are not intended for prolonged or repeated use. Such emergency hoods need to provide a wearer with protection for only fifteen minutes or so, preferably at least twenty minutes, to allow escape from a contaminated area. They generally comprise an oro-nasal mask, for fitting over the wearer's nose and mouth, and a hood (with neck dam) for fitting over the wearer's head. Air filters are connected to the oro-nasal mask. The hood may serve to protect the wearer's eyes and other facial, head and neck features, from hazardous chemicals.
In WO2007/042754, we disclosed such a filtration mask of respirator type, which had two filtration supports connected by an air guide containing two exhale valves, with a collapsible air guide mounted to the air guide between the filter supports. The filter supports were hinged to the air guide removable between the position in which the air guide was in a collapsed state, and the filter supports were close together to a deployed state in which the filter supports were further apart, and the air guide was deployed.